package nk;

import java.util.Scanner;

/**
 * 在其它数出现次数都为偶数的数组中找到出现次数为奇数次的数
 */
public class FindOneOddNum {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int count = in.nextInt();
        int ans = 0;
        for (int i = 0; i < count; i++) {
            ans ^= in.nextInt();
        }
        System.out.println(ans);
    }
}
